An angle accessory of that type is already known, in particular from Document IT 01281834. In that angle accessory, a flap has facing lugs at one end of its lips, those lugs carrying studs designed to be inserted into openings provided in the lips of the other flap.
The flaps are assembled together by pinching together slightly the lips of the flap carrying said openings so as to deform said lips elastically and so as to engage said openings over said studs.
Thus, said flaps can take up different relative angular positions between a first end position in which the flap carrying the studs uncovers the other flap to as large an extent as possible in order to form an angle less than or equal to 90°, and a second end position in which the flap carrying the studs is fully folded over onto the other flap to form an angle greater than 90°.
In addition, in that document, each of said lugs carrying the studs of the corresponding flap has a circular edge provided with a bevel which, when said flap is in the second end position fully folded over onto the other flap, serves to co-operate with a recessed wedge provided in the vicinity of the opening, on the outside surface of the lip of the corresponding flap. In said second position, that co-operation between the bevels and the wedges acts when an impact occurs on said flaps to prevent said studs from disengaging from said openings, and thus to prevent said flaps from coming apart.
The major drawback of the above-mentioned angle accessory is that, apart from the bevel and wedge arrangement, it has no means for acting, when said flaps are in relative angular positions other than said above-mentioned end position, to prevent impacts on said flaps from causing the studs to disengage from said openings and thus from causing said flaps to come apart.